This disclosure relates to the field of bone and tissue repair, and in particular to materials for bone and tissue repair, methods of making the materials, and methods for use of the materials.
Replacement and repair of bone and other tissues following injury often requires the use of surgical procedures. More than 300,000 hip prostheses are implanted each year in the United States and Europe. Additionally, 10% of the population suffers from periodontal disease, and 30% will require a tooth implant during his/her lifetime. Other surgical procedures include cartilage repair and plastic surgery of soft tissues. It is thus desirable to create scaffold materials for tissue repair or reconstruction, particularly injectable materials that can eliminate the need for many invasive procedures. Such materials should be biocompatible, i.e., not cytotoxic or causing adverse reaction in the body and preferably bioactive, i.e., providing the developmental signals needed for mobilization of the cell activity required for tissue building. They are furthermore preferably resorbable, and capable of withstanding the stresses imposed by daily activity during repair.
Several different approaches to scaffolds for tissue repair have been suggested. Currently available materials for hard tissue repair such as demineralized bone, hydroxyapatite, tricalcium phosphates, and other inorganic materials are not as effective as biologically derived bioactive scaffolds. Hyaluronic acid has been used as a scaffold material as disclosed in U.S. Pat. No. 5,939,323. Another approach has been to use collagen-based materials as disclosed in U.S. Pat. No. 4,490,984 and U.S. Pat. No. 5,480,644. These materials, however, appear to be limited in their range of potential uses and applications because of poor mechanical properties, unpredictable degradation rates and, for collagen, the risk of immunogenic reactions and dangers related to potential contamination.
Membranes, films and fabrics containing fibroin, a protein component of silkworm silk, have been suggested as substrate materials for the growth of animal tissues and organs. In particular, PCT Application number WO 01/25403 describes the formation of fibroin membranes cast from water solution. The membranes were cast in containers into which growth medium and various cell types were added, and the fibroin membrane supported the growth of cells such as osteoblasts, epithelial cells, and hepatocytes. Fibroin membranes and films are also disclosed by Tsukada et al., in Journal of Polymer Science: Part B: Polymer Physics 32: 961-968, 1994; and by Motta et al., in “Third International Symposium on Frontiers in Biomedical Polymers Including Polymer Therapeutics From Laboratory to Clinical Practice”, Abstract, Shigha Japan, May 1999. PCT Application WO 02/29141 describes the formation of fibroin non-woven fabrics made by treating fibroin cocoons with formic acid. The fibroin non-woven fabrics can be used to culture cells such as keratinocytes and fibroblasts. A drawback of using such fibroin membranes, films, or non-woven fabrics as a scaffolds for tissue repair in vivo is that invasive surgical procedures would be required in order to place the materials at the site to be restored.
Accordingly, there remains a need for bioactive scaffold materials for use both in vitro and in vivo, particularly materials that are biocompatible, bioactive, and resorbable. There further remains a need for bioactive scaffold materials that are readily applied to the site to be restored, preferably without use of invasive surgical procedures.